The invention relates to a steelmaking plant having electric arc furnaces which can be tapped at their bottoms.
Until now, it has been customary to form steelmaking plants or factories from individual steelmaking units, i.e., from electric arc furnaces, each such furnace unit being self-contained, i.e., having all the necessary components required for its operation.
It is an object of the invention, however, to increase the output of such a plant while keeping the investment costs approximately constant. The present invention is directed to a novel steelmaking plant which consists of several individual furnace vessels which are arranged on a single charging floor and each of which is provided with a tapping door which can be closed off. For the several vessels, (preferably two), only a single lid and only one electrical supply installation are provided, both of which are attached to a mobile supporting structure which can be alternatively positioned in the operating position above either of the vessels, as desired.
The present invention is premised on the background knowledge that the operator of an electric arc furnace installation ordinarily keeps a second reserve furnace vessel in complete readiness. When repairs, generally to the refractory lining, have to be carried out on the vessel which has been in operation, the reserve furnace is called into action. According to the present invention, this ordinarily reserve-only furnace vessel, which is unused most of the time, can be now called upon for increasing product output and for improving the efficiency of the operational process, without requiring any significantly additional expenditure. The present invention results in a furnace installation in which both vessels are used, alternately, in the course of normal operation. Should one of the vessels require repairs which last longer than expected, the other vessel is still always available for use, so that the output usually achieved with one vessel is at least produced during this period.
The alternating operation of two furnace vessels results in many advantages. These are, inter alia, that the lid and the electrodes do not cool off between changes and that energy losses, otherwise caused by this cooling off are eliminated. In addition, as a result of avoiding intermediate cooling, the furnace lid will exhibit longer service life since it will not be subject to as frequent periodic thermal changes. Moreover, a more uniform utilization of the power supply is achieved, because energy is consumed almost continuously, rather than periodic peaking due to high power drainage and total shut-downs.
Since each vessel is available after each charge, for the same period of time, about 2.5 hours, smaller repars can be carried out without particular time pressure. Moreover, scrap can be charged for a longer period of time before the furnace is energized and can be preheated by the retained heat radiating from the just used furnace vessel. Again, it can be seen that energy is saved.
When using the product of the present invention in a continuous casting plant, considerable advantages occur because the steel, provided by the steel furnaces of the present invention, sought to be cast is available at shorter intervals than heretofore present and, therefore, smaller intermediate vessels can be used.
The relatively uninterrupted operation of the present invention and the use of only a single lid for two furnace vessels is made especially possible by the fact that furnace vessels having bottom tapping mechanisms are used which, in contrast to the prior art furnace vessels which require tilting for tapping, i.e., the lid and its electrode attachments participated in the tilting motion, have lower relative investment cost, also allow for more rapid tapping possible, while, at the same time accomplishing this in considerably less space.